This present application is concerned with the field of polyimide-polyamide and lightweight flexible foams. More specifically, the application is concerned with foams resulting from the reaction of organic acids/anhydrides and polyisocyanates.
U.S. Pat. No. 3,300,420 teaches the preparation of foam resins from aromatic anhydrides and isocyanates. A high polyimide content foam and a lightweight flexible foam is not fully described.
U.S. Pat. No. 3,620,987 describes the reaction of polyisocyanates, with acids and anhydrides in the presence of epoxide groups. It is desired to prepare poured in place foams using a particular combination of catalysts, in particular, materials which catalyst the reaction between the isocyanate group and an active hydrogen atom such as those utilized in synthesizing polyurethanes. Various epoxy resins are described as useful in the reaction with the isocyanate and the anhydrides.
U.S. Pat. No. 4,738,990 describes a fireresistant foam composed of predominantly amide and imide linkages prepared utilizing a cyclic phosphorous catalyst. Heavy shrinkage of the resulting foam produced is undesirable.
It has been found that utilizing the cyclic triazine catalyst of the present invention in conjunction with utilization of multiple acid/anhydride reactants, one can achieve a lightweight, open-cell flexible foam with low shrinkage caused by the generation of carbon dioxide during the manufacturing process.